APDU

Application Protocol Data Unit.
An APDU contains either a command or a response. For the command APDUs, there are four cases:
• CLA INS P1 P2
• CLA INS P1 P2 L_c Data
• CLA INS P1 P2 L_e
• CLA INS P1 P2 L_c Data L_e

CLA is the Instruction class, INS the instruction byte, P1 P2 the instruction parameters, L_c the length of the instruction's data field, Data is the instruction's data field and L_e is the maximum number of bytes we expect in the response's data field.
The response APDU is coded as follows: Data SW1 SW2
Data is the response's data field and SW1 SW2 are the status bytes.

ATR

Answer To Reset.
Gives vital information concerning timings and voltages, and also historical information for the smart card. The ATR can be used to determine the type of card, since most card types have their own unique ATR.

CHV

Card Holder Verification.
A method of protecting a file with a PIN code or password. The CHV code is usually 8 bytes. Mapping a four digit PIN code to a CHV code may be different for different card systems.

CONVENTION

The convention determines how the bits that the card outputs and that are sent to the card are decoded. Two conventions are used:
direct
The bytes are interpreted the "normal" way as in standard serial port communication.

inverse
The bytes are complemented and reversed.

The inverse convention usually requires odd parity, while the direct convention requires even parity.

CLASS

Instructions can be grouped in an instruction class. This can be useful for multiple applications on one card or for testing purposes.

DF

Dedicated File. This file is similar to a directory and contains other files (EFs or other DFs). The top DF is called the MF.

EF

Elementary File. This file contains data. Working EFs are used for data that is not used by the card, but the outside world. Internal EFs are used to store data that is used by the card.
The following EF structures exist:
transparent
the file is a bag-o-bytes.

linear fixed
the file contains a sequence of records of fixed size.

linear variable
the file contains a sequence of records of variable size.

cyclic
the file contains a ring of records of fixed size.

ETU

Elementary Time Unit.
For cards with an external clock, this value depends on the clocking period provided on CLK. The initial etu value is 372 / f_i s, where f_i is the clocking frequency. For a 3.58 MHz clock, the etu will be 1/9600 s.

FCI

File Control Information.
Usually contains file length, file id, file type and file permissions.

FILE

The memory in a smart card is organized in files, just like a floppy disk. Two types of files exist:
• dedicated files (DF). These files are similar to directories. The DF at the root is called master file (MF).
• elementary files (_EF).

INSTRUCTION

One byte that tells the smart card what to do. The instruction is interpreted by the card's operating system. The instruction set can differ per card, there are a few standards: ISO 7816-4, ETSI TE-9, CEN en726-3, GSM 11.11.
Some standard instructions are:

MF

Master File. This is the root DF. Its file ID is always 3f00.

P1 P2

The instruction's parameters.
For example: specifying a certain key, wether or not to return file control information.

PROTOCOL

ISO 7816-3 defines a few transmission protocols. The protocols that a card offers can be extracted from the ATR. The following protocols are defined:

SW1 SW2

Status Word bytes. Encode the processing state in the card. The codes below are specified in ISO 7816-4. Some cards will use slightly or entirely different codes.

T=0

An asynchronous, half duplex, character transmission protocol.

T=1

An asynchronous, half duplex, block transmission protocol. Transmits APDUs in blocks and does error checking. It is more difficult to implement than T=0, but more convenient and more reliable.

TLV

Tag Length Value. An encoding mechanism that does not fix the size of an object. The tag denotes the type of data (e.g. FCI), the length denotes the length of the value field, i.e. the number of bytes that follow the length byte.
Example:

  ,-----+--------+----------------------------------------.
  |  63 |  0d    | 00 1e 1f 24 da c4 03 3f ff c1 02 03 03 |
  | TAG | LENGTH |        VALUE                           |
  `-----+--------+----------------------------------------'

©2002 Pro-Active. All rights reserved. SpringCard-CF and the Pro-Active logo are trade marks of Pro-Active.
Microsoft, Windows and the Windows CE logo are either registered trademarks or trademarks of Microsoft Corporation in the United States and / or other countries.